I'm going to start finishing the basement over xmas and need to put two openings in the load bearing wall, one for a standard size door (34 inch) and one for double french doors.

My questions are:

a) Do i need to put up temporary support when creating the two openings (before the header is in place, after studs are removed) ? I've had different contractors give me different answers. If i do need a temp support, does anyone have any links as to how i would built a temporary support ?

b) for the single door I'll want a 36 inch opening (34 inch door) and for the double door is it a 70 inch opening ?

a) Common sense would dictate that you need to temporarily support a load bearing wall prior to removing the existing support and reinstalling a permanent support header.
The temp supports would basically be ran perpendicular to the joists on either side of the wall that you plan to cut the opening in.

b) Doors come in a variety of widths so the RO (rough opening) would depend on the width of the double doors you install.